1. Field of the Invention
This invention lies in the field of document handling and reading apparatus and, more particularly, card reading apparatus for reading data processing cards.
2. Description of the Prior Art
In the field of card reading devices, there has been a long standing need to optimize the picking design so as to achieve two somewhat contradictory objectives. First, as is apparent, it is necessary to separate the cards which are to be fed through the equipment and processed, so as to make available one card at a time for processing purposes. Typically in the prior art this is done by transporting the cards through a defined space, or throat area, which is dimensioned so as to permit only one card at a time to pass therethrough. Clearly, if the throat dimension is just barely greater than one card thickness, and clearly less than the thickness of two combined cards, transport of only one card at a time is permitted. Viewing only this first consideration, the closer the throat thickness to simply one card thickness, the greater the separating ability of the card reader, and the less chance that a plurality of cards will be picked simultaneously. At contrast with this criterion is the design criterion of adjusting the throat so as to pass cards which are damaged or otherwise deformed such that their effective thickness is greater than that of the normal card. This is a very practical consideration, since in practice a typical card will have been processed through various pieces of data processing equipment a plurality of times, and statistically a certain number of such cards will become scuffed up, banged around and otherwise damaged so as to effectively increase the card thickness and make them unfit for transport through a throat having a separation of just barely one normal card thickness. In order to accommodate these two competing considerations, the throat separation will typically be set at about 1.5 card thicknesses. However, this compromise arrangement alone is less than totally satisfactory, particularly because it simply doesn't give sufficient allowance for the certain number of damaged cards which must be transported through the reader.
In addition to the above consideration, there is a great need for improvement in picking cards without altering or damaging the middle portion of the leading edge of the card. Most card readers sense the leading edge at its center, and develop basic timing signals from this sensing. Damage to the leading edge, aside from card thickness variations, can alter the very sensitive timing signals. In particular, it has been found that for card readers where the card is fed lengthwise through the throat, prior art systems remain unreliable and are unsatisfactory in the handling of initially undamaged cards. As used hereinabove, the term sidewise feeding refers to feeding the card through the throat such that the leading and trailing edges constitute the longer edges of a rectangular card or document. The term lengthwise refers to feeding the cards such that the two shorter edges are the leading and trailing edges respectively.
As important as it is not to damage the leading edge of the cards fed through a card reader, it is even more important not to damage the stored information, i.e., the punched holes or the marks. In order to prevent ripping of the holes, or smudging or double printing of the marks, it is necessary to minimize contact of the card reader transport system with the holes or marks. This criterion calls for an integrated system design which permits the card to be transported from feed bin to receiving bin with such minimum contact.